The design of chairs, and particularly of office chairs, has been given attention in recent years; so-called "ergonometric" models were provided in which great effort has been expended to match the seat configuration to the human anatomy of users. Specific attention has been given to adjustability of the seat and the back rest, synchronization of movement of seat and back seat, and relative change of adjustment between seat and back rest.
Chairs, and especially office chairs, are increasingly used for extended periods of time. Chairs are sold essentially only in "one size fits all" configurations, based essentially on their intended use. No attention has been given to the design of the chair itself with respect to matching the configuration of the chair to the anatomy, size, and limb configuration of the users. Even automobile seats are adjustable only with respect to operating controls of the vehicle; a few permit adjustment of lumbar supports; the overall size and configuration of the chair, however, is invarying for all users, tall or short.
It is an object of the present invention to improve arm chairs, particularly office chairs, so that the comfort of the user is enhanced.
Briefly, the arm rests are constructed to be height-adjustable with respect to the seat of the chair. The arm rests are pivotably connected to the chair seat or chair seat support structure adjacent to or close to the forward edge of the seat, and supported, height-adjustably, in a region adjacent the chair back.
The invention is based on the realization that chairs should be useful for persons of widely differing sizes and widely differing relationships of trunk size to limbs; thus, the chair should be equally comfortable for persons with short trunks and long arms as for persons with long trunks and short arms. Experiments have shown that proper relationship of the arm rest of a chair is of substantial importance for the comfort of the user. Surprisingly, it has been found that already slight difference in the level of arm rests with respect to the chair seat are of substantial importance for the user's comfort and seating satisfaction. If the arm rests are too low with respect to the shoulder position of the user, which would occur if a user has a long trunk and short upper arm bone structure, the user has a tendency to lean, leading to poor posture when seated, and, over an extended period of time, to damage due to the poor posture. If the arm rests are too high with respect to the shoulder position of the user, the user has the tendency not to use the arm rest at all or, again, to tilt upwardly in the seat against the arm rests which interferes with seating comfort. When the arms rests have the appropriate height, they are used more, and properly, by the seated person. Periodic raising by bracing against the arm rests leads to periodic unloading of the spinal column which, surprisingly, substantially improves the seating satisfaction of the user. The user is much less subject to tiredness, cramps in back muscles, back pain, and the like, if the height of the arm rest is matched to the anatomical configuration of the user.
In accordance with a preferred embodiment of the invention, the respective arm rests are supported by support elements which are adjustable in their length. This permits a simple construction of pleasing appearance. Changing the length of the support element can be simple by constructing the support element with a thread which engages with a thread of the carrier or in an adjustment nut. Simple height adjustment by merely rotating the carrier element or the adjustment nut, respectively, is thus possible. In accordance with a preferred feature of the invention, the support element is a two-part bolt structure, each bolt structure carrying, respectively, a right-hand thread and a left-hand thread, coupled together by an adjustment nut with matching threads. This arrangement permits rapid adjustment of the height of the support element and doubling of the possible height adjustment for a given rotation of the adjustment nut. Preferably, the adjustment nut is an elongated sleeve fitting over the threaded portions of the bolt elements which is readily accessible for rotation. The sleeve covers the threaded portions of the bolt elements, which is desirable from an appearance point of view and prevents contamination of the thread elements, or casual contact therewith by the user.
In accordance with a further preferred feature of the invention, a stop arrangement, for example a snap ring or the like, is located within the adjustment nut or sleeve to limit the height adjustment and prevent excessive rotation of the adjustment nut or sleeve by a careless user, thereby releasing the threaded support elements or bolt elements from the adjustment nut. A scale can be located on one of the bolt elements so that a desired position can readily be obtained again after adjustment, for example by a different user. This scale can indicate the degree of adjustment or of respective positions.
In accordance with a preferred feature of the invention, the arm rests are bent downwardly adjacent the forward edge of the seat and pivotably connected to the seat or its support structure by laterally adjustable carrier or support elements. The rearward portion of the arm rests are secured to upwardly extending support rods, adjustable as described above, which, in turn, are pivotably connected near the chair back or adjacent thereto to the seat or the seat support structure. This results in a simple construction of pleasing appearance. By pivotably connecting the support elements for the arm rests and the arm rests themselves, respectively, adjacent the rear and forward portion of the seat, pivot connections can be used which, preferably, can be laterally adjusted with respect to the seat so that users of narrow shoulder width can move the arm rests close towards the seat, whereas users with wide shoulders can spread the arm rests out by increasing the horizontal spacing between the arm rests, so that they are universally adjustable, both with respect to height as well as spacing in relation to the seat, and hence to the anatomy of the user.
Bending the arm rests to merge at their forward sides close to the seat not only provides for pleasing appearance of the chair but additionally permits fitting the chair beneath furniture, such as tables or desks, without impinging on desk drawers or other structural elements of other furniture components.